1. Field of the Invention (Technical Field)
The presently claimed invention relates to oil and gas well servicing and more particularly to a flowback and separation system for controlling the flow of fluids into the separation system, the separation system provides for separation of gas, well bore cuttings, produced oil, and produced water to be automatically separated. The gas can be sold or recirculated for reuse in the flowback operation.
2. Background Art
In a traditional prior art flowback operation, the pressurized transport gas, well cuttings, produced oil, and produced water are brought back to the surface into an open top tank. A mist of produced oil and water is produced by the nozzle effect of the fluid entering the tank and carried into the atmosphere causing environmental release complications. Additionally, if natural gas is used as the transport gas, the gas is released into the atmosphere, or diverted to a flare stack.
An alternative, newer method of flowback is conducted through the use of a high pressure “sandbuster” vessel used to remove the solid products carried up from the well bore from the process stream followed by a small volume pressure vessel used to separate the gas phase from the liquid phase. The produced water and produced oil liquid mixture is then emptied through process piping to a holding tank. The gas phase is released through process piping to a flare stack or reused for the well servicing operation. This system can accommodate a closed loop flowback operation; however, it is limited in the range of process conditions it can accommodate, does not provide the data collection and automated correction of the blast choke, does not allow for separation of the oil and water liquid phases, and does not incorporate any significant automation.
The above approach uses a small volume pressure vessel. Manufacturing a large vessel capable of withstanding high pressure is difficult and expensive. The small volume pressure vessel cannot handle a large slug of liquid and cannot separate the liquid into the oil and water phases in the vessel. This limitation creates additional expense for additional equipment and tanks on site. The additional equipment also adds an additional safety hazard associated with the congestion on the well location.
In addition to the approaches taken above, others have attempted to monitor the erosion status of the restriction choke by measuring the pressure upstream and downstream of the restriction choke and charting this pressure trend on a pen chart recorder. The trend is observed by a technician and compared to pre-determined charts to make a judgment determination to change the choke restriction. No automation is used to mitigate the safety hazards associated with human interaction with the system. An example of the prior art systems as discussed above can be found at:
http://www.ipsadvantage.com/production_testing.html
There are significant disadvantages of the aforementioned open tank flowback systems. These include environmental release associated with the mist of fluid exiting the top of the tank, waste and potential environmental release associated with venting the transport gas to the flare stack, the inability to monitor the erosion status of the choke restriction or to change the choke restriction and to separate the process fluids, in real-time.
The disadvantages of the small volume pressure vessel flowback systems include: waste and potential environmental release associated with venting the transport gas to the flare stack, inability to monitor the erosion status of the choke restriction, reliance on the judgment of the technician on when to change or check the choke restriction, the small volume pressure vessel can “slug” or be overtaken by liquid when a large slug of liquid surges through the wellbore to the surface. The small volume tank cannot empty fast enough to accommodate the sudden intake of liquid, is unable to open and close valves to divert the process fluid flow through an automated system to accommodate the changing flow conditions, unable to monitor from a safe distance or remotely monitor the status of the flowback operation, and unable to adjust an automatic choke using inputs from an automation system, in real-time. The prior art devices are unable to incorporate automated safety shut down or ESD systems by monitoring data being transmitted by sensors and predetermined programmed safety perimeters by interpreting the data being monitored. They are also unable to automatically divert flow to an alternate blast barrel or blast choke from data being monitored.
State of the art approaches have failed to solve the problem through lack of automation, limitations on the range of flow parameters, and inability to fully separate process fluids. The inability to accurately determine the erosion status of the choke restriction can result in safety hazards and potential environmental release. Additionally, the lack of automation prevents these approaches from automatically diverting flow to separate choke restriction lines or tanks, depending on the flow conditions. The lack of automation also prevents these approaches from monitoring and controlling the system from a safe distance. These existing systems do not provide the ability to modify or remotely monitor the choke setting through the use of an automatically adjustable blast choke integrated into the system. Additionally, existing systems have failed to address the numerous advantages associated with the ability to remotely monitor or automatically control the choke setting, providing a much higher level of control and safety over the flowback operation. Finally, existing systems have failed to address the problems caused by their lack of range ability. The existing systems fail to work when the well bore sends a large slug of liquid to the surface, causing the existing small volume tanks to flood out.